In a recent article Mabee et al. [2012, Energy Policy 40 (1), 480–489] describe the German legislation to promote renewable electricity generation (Erneuerbare-Energien-Gesetz). The erroneous assumption that anannual degression of feed-in tariffs for any given power generating facility are stipulated in the law leads to wrong calculation of net present values of the revenues tream. Reduction of feed-in tariff rates only holds for new additions. There is however one exception in offshore wind energy where the operator can opt for a degression. The implications of the newly introduced option are discussed in this comment.